The Journal’s ad revenue wasn’t affected by its recent drop in Google traffic because social media visits grew 34 percent in that time, keeping overall web traffic flat, Watford said.
Their numbers agree with your hypothesis: people simply switched from using the (now closed) Google "payhole" to the social media "payhole."
Their numbers agree with your hypothesis: people simply switched from using the (now closed) Google "payhole" to the social media "payhole."